Sony PSP3 not 100% backwards compatible?

Joystiq claims the backwards compatibility of the PlayStation 3 may not be as certain as it once was.

Software emulation is the same trick being used by the Xbox 360 to play original Xbox title, and Microsoft is still trying to get its back catalogue to function properly (as of today, our beloved Psychonauts is still not playable on our shiny 360 consoles). The source claims that "a surprising number of PS2 titles are already working on PS3 prototype hardware." Sony must get the majority of its back catalogue compatible with the new PlayStation or they will lose one of their key speaking points.